1. Field of the Invention
The present invention relates to a toner used for an image forming in an electrostatic copying process of a copying machine, facsimile or printer.
2. Description of the Related Art
In the image forming apparatus for the electrophotography, a toner image is formed on the photoconductor through the steps comprising charging the surface of the photoconductor which is a carrier of the image by the discharge, exposing the surface of the charged photoconductor for forming a latent electrostatic image on the surface of the photoconductor and developing the latent electrostatic image formed on the surface of the photoconductor by supplying a toner having a polarity which is reverse to the polarity of the latent static image formed on the surface of the photoconductor to the latent static image. The toner image formed on the photoconductor is, thereafter, transferred to an intermediate transferring medium temporary and is either transferred to a recording member, such as a paper from the intermediate transferring medium, or through transferring the toner image from the photoconductor directly to the recording medium, fixed on the recording medium by applying heat and pressure to the transferred toner image on the recording medium.
In the above-noted fixing step, the recording member is put between a pair of fixing members in the form of a roller or a belt which are equipped with a heater in the inside thereof and the toner is molten by the heating and pressed, so that the toner image is fixed on the recording member. At this time, when the heating temperature of the toner is too high, the toner is fused excessively and a disadvantage is caused that the toner is fused to the fixing member (hot offset). On the other hand, when the heating temperature is too low, the toner is not satisfactorily fused and a disadvantage is caused that the fixing itself becomes unsatisfactory. From the viewpoint of saving the energy and the downsize of the image forming apparatus, a toner having high resistance to the hot offset (i.e., the hot offset of a toner is caused at a high temperature) and the low temperature image fixing properties (i.e., a toner can be fixed at a low temperature) is required. It is also necessary that the toner is not blocked either during the storage of the toner or at the temperature of the atmosphere in the image forming apparatus (i.e., the toner has high resistance to the blocking).
Particularly, in the full-color copying machine and the full-color printer, it is necessary that the image has high glossiness and high mixed-color properties and the toner has accordingly a low molten viscosity, so that as a component of the toner, a toner binder of a polyester resin having sharp melt properties. Since in using such a toner, the hot off-set is easily caused, conventionally in the apparatus for the full-color, the fixing member is coated with a silicone oil. However, for coating the fixing member with the silicone oil, an oil tank and an oil coating unit are necessary, so that the image forming apparatus becomes complicated and large. Also, the deterioration of the fixing member is caused, so that a maintenance of every fixed period becomes necessary. Further, the silicone oil is inevitably attached to a paper for the copying or a film for OHP (over head projector) and particularly with respect to OHP, the tone of the image is impaired due to the attached silicone oil.
Thus, for preventing the fusion of the toner without coating the fixing member with the silicone oil, generally a method of mixing the toner with a wax is used. However, the releasing effect of the wax varies largely depending on the dispersion condition of the wax in the binder resin of the toner.
In Japanese Patent (JP-B) No. 2663016, it is described that by producing the toner through a suspension polymerization of a substance having a polar group with a polymerizable monomer composition comprising a releasing agent in water, a wax having a low melting point which cannot be used in the toner produced by a grinding manufacturing method, can be incorporated in the composition of. It is considered that a non-polar component, such as a wax is not present in the surface of the toner particles, on the contrary to a polar component, but present in such a pseudo-capsule structure that the non-polar component is covered by a polar component which is present in the surface of the toner particles. However, the distribution of the wax in the inside of the toner particle is not yet analyzed and is unclear.
In JP-B No. 3225889, described is a toner in which the amount of the wax is 0.1% by mass to 40% by mass, based on the mass of the toner composition and the ratio of the mass of the wax which is present in the surface of the toner particles to the mass of all components of the toner composition which are present in the surface of the toner particles is 1% by mass to 10% by mass. In this patent document, the ratio of the wax which is present in the surface of the toner particles is defined by measuring the above-noted ratio of the wax using ESCA. However, the range of the ESCA analysis is restricted to a range of from the outermost surface of the toner particle to the depth of around 0.1 μm in the toner particle, so that by the ESCA analysis, the dispersion condition of the wax which is present in a deeper portion of the toner particle than the depth of around 0.1 μm and which exhibits releasing properties during fixing an image, cannot be clarified.
In Japanese Patent Application Laid-Open (JP-A) No. 2002-6541, described is a toner in which the wax is involved in the toner particle and is localized in the surface of the toner particle. However, in this patent document, the detailed dispersion condition of the wax around the surface of the toner particle is unclear.